Variable speed drive for mechanical stokers



Feb. 16, 1937. 5, SKELLY 2,070,756

VARIABLE SPEED DRIVE FOR MECHANICAL STOKERS Filed Jan, 10, 1934 2Sheets-Sheet l Feb. 16, 1937 J. 5. SKELLY 2,070,756

VARIABLE SPEED DRIVE FOR MECHANICAL STOKERS Filed Jan. 10, 1934 2Sheets-Sheet 2 UNITED STATES PATENT OFFICE VARIABLE SPEED DRIVE FORMECHANICAL STOKERS John S. Skelly, Monongahela, Pa.

Application January 10, 1934, Serial No. 706,040

9 Claims.

This invention relates to mechanical stokers, and more particularly tovariable speed drives therefor.

An object of this invention is the provision of means for adjusting thespeed of operation of the fuel feeding apparatus employed in mechanicalstokers without changing the speed of operation of the driving motor orof the speed of operation of the forced draft fan driven thereby.

Another object of the invention is the provision of an adjustable speeddrive for stoker fuel-feeding mechanism, whereby a large numbr ofdifferent operating speeds may be obtained without the use of speedchange gears or variable speed gear transmission, or without changingthe fan and motor speeds.

Other objects of the invention will, in part, be apparent, and will, inpart, be obvious from the following description taken in conjunctionwith the accompanying drawings in which:

Figure 1 is a view in side elevation of a mechanical stoker providedwith an adjustable speed drive for the fuel-feeding mechanism andembodying one form of the invention;

Fig. 2 is a view, in elevation, of the front end of the stoker showingthe adjustable speed drive;

Fig. 3 is an enlarged, fragmentary view, partially in section, showingthe mechanism employed for adjusting the speed of operation of the fuelfeeding mechanism;

Fig. 4 is a view in elevation, and partly in section, of the front endof the apparatus shown in Fig. 3; and

Figs. 5 and 6 are top plan views showing an adjustable speed elementembodied in the variable speed drive in its minimum and maximum speedsettings.

Throughout the drawings and the specification, like reference charactersindicate like parts.

In Fig; l of the drawings, a mechanical stoker assembly I is illustratedto which an adjustable speed drive 2 for the fuel feeding mechanism isapplied. Enlarged views of this drive are shown in Figs. 3 and 4. Thestoker illustrated is of the underfeed type and comprises, in general,an air chamber or box 3 in which a retort (not shown) is disposed. A rowof tuyere blocks 4 is supported on the top of the one side of the airbox and these blocks are formed with openings 5 through which combustionair discharges from the air box to the combustion space at the top ofthe retort. The particular type of construction embodying the airchamber, retort and tuyere blocks herein shown, is illustrated in detailin my copending application, Ser. No. 677,981, filed June 28, 1933.

Fuel is delivered to the retort above-mentioned from a hopper ormagazine 1 by means of a screw conveyor 8 disposed in a housing 9. Thisconveyor delivers the fuel to the retort through an opening (not shown)in the front end thereof. 5

The feed screw or conveyor 8 is driven by a motor I0 illustrated as anelectric motor, the motor being coupled thereto by means of theadjustable drive mechanism 2 and a gear reduction mechanism II, thelatter mechanism being often 10 denominated a speed reducer.

' The motor is stationarily mounted on a support frame or table l2.

The combustion air delivered to the air chamber or box 3 is supplied bya forced draft fan I3 15 driven by motor In. As illustrated, the fan isdirectly connected to a shaft ll of the motor and therefore operates atthe same speed as the motor shaft.

It is generally known that fans or blowers, of the type above-mentioned,to be eflicient must operate at relatively high speed and for the sizeof blowers employed on stokers of this type, the fan speed is on theorder of 1700 to 1800 R. P. M., and motors operating at these speedshappen to be the most practical for the type of apparatus hereinillustrated.

It is therefore important that the adjustable speed drive for the fuelfeeding mechanism be so arranged that speed adjustments may be madewithout changing the speed of operation of the motor or the position ofthe motor with respect to the fan.

It is appreciated that in the prior art, speed change gears oradjustable speed transmissions have been employed whereby the speed ofoperation of the fuel feeding mechanism could be adjusted withoutchanging the position of the motor, but such speed adjusting drives werecomplicated, expensive, and did not provide a wide range of speedadjustments nor a wide number of speed settings between the maximum andminimum running speeds.

The adjustable speed drive herein contemplated makes possible anydesired or practical number of speed adjustments without shifting theposition of the motor or changing gears, is simple in construction, andrelatively inexpensive compared to the speed change gear transmissionsabove mentioned.

The adjustable drive above mentioned, comprises a jack shaft orcountershaft l6, which is journaled in a bearing housing or. support 11,that is movably mounted on and secured to a support l8, which is hingedat one end on a bearing pin l9. As shown, support H has a portion 11extending through an elongated opening'O in support l8' and is slidablysecured to support I8 by a plate P secured to portion l1 and spanningthe opening 0.

Motor III has a driving connection with the jack shaft l 6 that includesgrooved pulleys 20 and 2| secured to the motor shaft and jack shaft,respectively, and an endless belt 22. This belt is held taut at alltimes by means of a compression spring 23 that acts on top of thesupport l8 urging pulley 2| in such direction as to exert a pull on thebelt. The weight of support l8, jack shaft 16 and bearing housing I!alsoaids in the maintenance of the proper tension in -belt 22. Insteadof a compression spring, a counterweight may be employed to maintain theproper tension in driving belt 22.

The driving connection between the jack shaft l3 and the speed reducerll includes pulleys 24 and 25, one of which is an adjustable effectivediameter pulley and a belt 26. As shown, pulley 24 is mounted on thejack shaft, and is the one whose eifective diameter may be adjusted,while pulley 25 is mounted on the power input shaft 21 of the speedreducer. By shifting the position of bearing -housing I'I in alongitudinal direction of support l8, the diameter of pulley 24 may beadjusted to thereby adjust the speed of operation of the power take-offshaft 28 of the speed reducer. Since the take-off shaft is connected tothe feed screw 8, the speed of operation of the feed screw may beadjusted.

Before giving a detailed description of the adiustable speed drivemechanism 2, the mechanism embodied in the speed reducer, as shown inFig. 3, will be briefly described.

As shown in Fig. 3, the power input shaft 21 has a worm 30 thereon thatmeshes with a worm gear 3| secured to a jack shaft 32 on which a pinion33 is mounted. This pinion meshes with a gear 34 secured to the outputor power take-off shaft 28 of the speed reducer. A wobble plate cam 35is mounted on the power take-off shaft for operating a reciprocating bar36 which is provided with a roller 31 that operates in a groove 38 ofthe wobble plate. The reciprocating bar is attached to distributing andagitating mechanism (not shown) disposed within the retort, and thisconstruction is also illustrated in my above-mentioned copendingapplication.

The adjustable speed drive mechanism is illustrated more clearly in theenlarged views of Figs. 3 to 6, inclusive. As shown in Figs. 4, 5,and-6, the adjustable diameter pulley 24 comprises discs 39 and 48having tapered working faces 4| which frictionally engage the oppositeedges of the driving belt 26. Disc 39 is stationarily mounted on jackshaft 16 while disc 40 is slidably mounted of the belt engage thesediscs relatively close to the jack shaft so that in effect, a pulley ofsmall diameter drives pulley 25 through the belt 26. When these discsare brought together to the position shown in Fig. 6 so that the beltengages the periphery of these discs, the largest working diameter ofthe pulley is brought into play, so

that'a pulley of relatively large diameter drives pulley 25 through belt26. By moving the bearin support I I longitudinally of the hingedsupport IS, the diameter of the pulley 24 may be varied in small steps.

If pulley 24 is moved in the direction of arrow A in Fig. 3, theincreased tension imposed on belt 26 causes the plates to separate apredetermined amount; and if the pulley is moved in the direction ofarrow B, the tension on the belt is relieved so that the compressionspring 42 will force plate or disc 40 towards the stationary disc andthereby increase the effective diameter of the pulley. By shifting thesupport, in which the jack shaft I6 'is joumaled, longitudinally of thesupport, the

above-mentioned changes in diameter of the pulley may be effected.

In Fig. 3, a convenient mechanism has been shown'for changing thediameter of pulley 24 in the manner above described. This mechanismcomprises a lever 46 having a pawl 41 thereon cooperating with astationary ratchet 48. This lever is attached to a shaft 49 to which anarm 56 is attached. Arm 50 is connected to the jack shaft bearingsupport or housing by means of a link 5 I. If lever '46 is moved toposition C in Fig. 3, the effective diameter of pulley 24 is adjusted toits greatest effective value and this represents the maximum drivingspeed of the fuel feeding mechanism. By shifting lever 46 to position Din Figs.

1 and 3, pulley I4 is adjusted to its smallest diameter and thereforethe fuel feeding mechanism will operate at its minimum speed. If lever46 is set in any position intermediate, that is in any positionsintermediate C and D, the speed of operation will be at a valueintermediate the minimum and maximum operating speeds.

When the adjustable support I! is shifted as above described, the jackshaft l6 moves or swings in the arc of a circle, the center of which isat the center of the motor shaft I4, and the proper tension ismaintained in the driving belt 22. The jack shaft swings in the arc of acircle because support I8 is hinged at one end; therefore, the free endof the support may move up or down according to the position it mustmaintain to provide the necessary tension in belt 22.

While the adjustable efiective diameter pulley 24 has been shown asmounted on the jack shaft l6, it will be apparent that this pulley mayas well be mounted on the power input shaft of the speed reducer II. Thechange in centers between the jack shaft l6 and the power input shaft 21is what effects the change in the effective diameter of the pulley 24;therefore whichever shaft pulley 24 is mounted on, the change ineffective diameter of the pulley may be efiected by changing thedistance between the centers of these shafts.

While but a single form of the invention has been shown and describedherein, it will be appreciated by those skilled in this art that variousmodifications and changes may be made without departing from thespiritor scope of the invention. It is desired, therefore, that onlysuch limitations shall be placed on the invention as are imposed by theprior art and the appended claims.

What I claim as new and desire to secure by Letters Patent is:

1. In an adjustable speed drive for mechanical feed stokers, thecombination with a. motor a and a gear reduction mechanism adapted to beconnected to the fuel feeding mechanism of the stoker, of a movablebearing having a countershaft iournalled therein, a pulley on the motorshaft, a pulley on said countershaft and a belt for said pulleys, meansfor maintaining a substantially constant tension in said belt, a drivingpulley for the gear reduction mechanism, an adjustable effectivediameter pulley on the countershaft, a belt connecting said drivingpulley and the adjustable effective-diameter pulley, and means forshifting the position of said movable bearing to vary the effectivediameter of the adjustable pulley and thereby adjust the speed ofoperation of said fuel feeding mechanism.

2. In an adjustable speed drive for mechanical feed stokers, thecombination with a motor, and a gear reduction mechanism adapted todrive the feed mechanism ofa stoker, of a variable speed drive betweensaid gear reduction mechanism and the motor comprising a movable bearinghaving a countershaft journalled therein, a pulley and belt connectionbetween said motor and countershaft, a belt and pulley connectionbetween the countershaft and gear reduction mechanism including anadjustable effective diameter pulley, means for shifting said movablebearing to change the effective diameter of said adjustable effectivediameter pulley and thereby adjust the speed of operation of the fuel'feeding mechanism, and means for maintaining a sub stantially constanttension in the belt of the belt and pulley connection between the motorand.

countershaft.

. 3. In an adjustable speed drive for mechanical feed stokers, thecombination with a motor, and a gear reduction mechanism having itsdriven member connected to the fuel feeding mechanism, of an adjustablespeed drive between said motor and gear reduction mechanism, comprisinga hinged support, a bearing housing movably mounted on the support, acountershaft journalled in said housing, a belt and pulley connectionbetween the motor and countershaft, an adjustable effective diameterpulley on said countershaft, a drive pulley for said gear reductionmechanism, a belt running on said adjustable effective diameter pulleyand said drive pulley, and means including a crank-arm connected to thehousing and a lever for moving the hearing housing on its support tothereby adjust the effective diameter of said adjustableeffectivediameter pulley and the speed of operation of the fuel feedingmechanism.

4. In an adjustable speed drive for mechanical feed stokers, thecombination with a motor, and a gear reduction meihanism having itsdriven member connected to the feeding mechanism, of an adjustable speeddrive between said motor and gear reduction mechanism, comprising ahinged support, a bearing housing movably mounted on the support, acountershaft journailed in said housing, a belt and pulley connectionbetween the motor and countershaft, a driving connection between thecountershaft and gear reduction mechanism including at least two pulleysand a belt, one of which pulleys is an adjustable eifective diameterpulley, and means for shifting said bearing housing to thereby adjustthe eifective diameter of said adjustable effective-diameter pulley, andthe speed of operation of said fuel feeding mechanism.

5. A variable speed drive for coupling a motor to an element to bedriven by said motor comprising a hinged support having a. bearingslidably mounted thereon, a jack-shaft journaled in said bearing, fixeddiameter pulley on said latter pulleys, and means for shifting thejackshaft bearing on its support to either increase or decrease theefiective diameter of said adjustable effective-diameter pulley.

6. A variable speed drive for'coupling a motor to an element to bedriven by-said motor comprising a hinged support having a bearingslidably mounted thereon, a jack-shaft journaled in said bearing, afixed diameter pulley on said jack-shaft, a fixed diameter pulley on themotor shaft, and a driving belt connecting said pulleys; an adjustableeffective-diameter pulley on said jack-shaft, a fixed diameter pulleycoupled to said driven element, a belt connecting said latter pulleys,means for maintaining a substantially constant tension in the drivingbelt, and means for shifting the jack-shaft bearing on its support toeither increase or decrease the effective diameter of said adjustableeffective-diameter pulley.

7. A variable speed drive for coupling a motor to an element to bedriven by said motor comprising a hinged support having a bearingslidably mounted thereon, a jack-shaft journaled in said bearing, afixed diameter pulley on said jack-shaft, a fixed diameter pulley on themotor shaft, and a driving belt connecting said pulleys; an adjustableeffective-diameter pulley on said jack-shaft, a fixed diameter pulleycoupled to said driven element, a belt connecting said latterpulleys,means for adjusting the tension in the driving belt, means formaintaining the adjusted tension in the driving belt substantiallyconstant, and means for shifting the jack-shaft bearing on its supportto either increase or decrease the effective diameter of said adjustableeffective diameter pulley.

8. A variable speed drive for coupling a motor to an element to bedriven by said motor comprising a hinged support having a bearingslidably mounted thereon, a jack-shaft journaled in said bearing, afixed diameter pulley on said shaft, a fixed diameter pulley on themotor shaft, and a driving belt connecting said pulleys; a second pulleyon said jack-shaft, a pulley coupled to the driven element, one ofsaidlatter pulleys being an adjustable effective-diameter pulley, a beltconnecting said latter pulleys, and means for shifting the jack-shaftbearing on its support to either increase or decrease the effectivediameter of the adjustable effective-diameter pulley.

9. A variable speed drive for coupling a motor to an element to bedriven by said motor comprising a movable support having a bearingslidably mounted thereon, a jack-shaft journaled in said bearing, fixeddiameter pulleys on said shaft, a fixed diameter pulley on the motorshaft, and a driving belt connecting said pulleys; a second pulley onsaid jack-shaft, a pulley coupled to the driven element, one of saidlatter pulleys being an adjustable efiective diameter pulley, a beltconnecting said latter pulleys, means for maintaining the tension in thedriving belt substantially constant, and means ,for shifting thejackshaft bearing on its support to either increase

